DC-DC feedback resistor calculator
Solve the feedback divider for an adjustable converter: enter the output voltage you want and the reference voltage, and read the standard E24 resistor pair.
Converter feedback divider
Results
Divider ratio (R1/R2)
Vout/Vref − 1
Lower resistor R2
Standard value picked from 1 k–100 k
Upper resistor R1 (exact)
R2 × (Vout/Vref − 1)
Upper resistor R1 (E24)
Nearest standard E24 value
Feedback current
Vout / (R1 + R2)
Divider power
Vout² / (R1 + R2)
Ratio R1/R2 = 3.13 (target 3.13)
About the divider
Feedback dividers sit between the output rail and the regulator's Vref pin. Keep R1 and R2 in the 1 k–100 k range: too low wastes power and loads the rail, too high lets noise and the reference input leakage skew the set point. The E24 proposal shows the standard-value option plus its percent deviation from the exact resistance, so you can judge whether the nearest E24 pair is close enough or should be fine-tuned with a second resistor.
Browse related parts:
Frequently asked questions
How do I set the output voltage of an adjustable DC-DC converter?
Most adjustable converters regulate against a reference pin: Vout = Vref × (1 + R1/R2). For a 0.8 V reference and a 3.3 V rail, the ratio R1/R2 = 3.3/0.8 − 1 = 3.125. The tool steps through standard R2 values from 1 kΩ up and reports the first pair that keeps R1 in range — with the defaults that is R2 = 1 kΩ, R1 = 3.125 kΩ, and the nearest E24 value for R1 is 3 kΩ (about −4%).
What resistor values should I use for the feedback divider?
Keep R1 and R2 in the 1 k–100 k range. Too low wastes power and loads the rail; too high lets noise and the reference input leakage shift the set point. The tool tries standard lower resistors from 1 k up and reports the feedback current and divider power so you can judge the trade-off.
How much does the nearest E24 resistor change the output voltage?
The output tracks the divider ratio, so the E24 deviation in R1 changes Vout by roughly the same percentage — a −4% R1 error (3 kΩ for the exact 3.125 kΩ) shifts a 3.3 V rail to about 3.2 V. When that matters, combine two standard resistors in series or parallel to hit the exact ratio, or use 0.1% precision resistors.
ICBOMS provides this tool for reference only.